The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Plasma arc torches, also known as electric arc torches, are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward the workpiece. Plasma arc torches, also known as electric arc torches, are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward the workpiece. In a typical plasma arc torch, the gas to be ionized is supplied to a distal end of the torch and flows past an electrode before exiting through an orifice in the tip, or nozzle, of the plasma arc torch. The electrode has a relatively negative potential and operates as a cathode. Conversely, the torch tip constitutes a relatively positive potential and operates as an anode. Further, the electrode is in a spaced relationship with the tip, thereby creating a gap, at the distal end of the torch. In operation, a pilot arc is created in the gap between the electrode and the tip, which heats and subsequently ionizes the gas. Further, the ionized gas is blown out of the torch and appears as a plasma stream that extends distally off the tip. As the distal end of the torch is moved to a position close to the workpiece, the arc jumps or transfers from the torch tip to the workpiece because the impedance of the workpiece to ground is lower than the impedance of the torch tip to ground. Accordingly, the workpiece serves as the anode, and the plasma arc torch is operated in a “transferred arc” mode.
In automated plasma arc torch applications, the plasma arc torch operates at current levels between approximately 30 amps and 1,000 amps or more. A relatively high voltage (HV) start circuit is applied to generate a pilot arc between the electrode and the tip. In a typical hand system, the HV generating circuit is in the power supply and the entire torch lead (with its associated capacitance) must be charged up to obtain a HV signal at the torch tip to start the arc. As a result, the power supply and the entire torch lead radiate energy into the surroundings, thereby generating noise in the power supply and surrounding electronic systems. In an automated system, the HV generating circuit may be provided at or near the torch head to reduce the length of the circulating path for the HV current. However, a large inductor is generally provided in series with the electrode or tip lead to isolate the HV generating circuit from the torch lead and results in a relatively large HV circuit that still radiates energy and noises to the surrounding environment.